Study of the $ϕ$ decays into $π^0π^0γ$ and $ηπ^0γ$ final states

Abstract

Radiative decays of the $ϕ$ meson have been studied using a data sample of about 19 million $ϕ$ decays collected by the CMD-2 detector at VEPP-2M collider in Novosibirsk. From selected $e^+e^-\toπ^{0}π^{0}γ$ and $e^+e^-\toηπ^{0}γ$ events the following model independent results have been obtained: \par $Br(ϕ\toπ^{0}π^{0}γ) = (0.92\pm 0.08\pm0.06)\times10^{-4}$ for $M_{π^{0}π^{0}}>700$ MeV, \par $Br(ϕ\toηπ^{0}γ) = (0.90\pm 0.24\pm 0.10)\times10^{-4}$. It is shown that the intermediate mechanism $f_{0}(980)γ$ dominates in the $ϕ\toπ^{0}π^{0}γ$ decay and the corresponding branching ratio is \par $Br(ϕ\to f_{0}(980)γ)=(2.90\pm 0.21\pm1.54)\times10^{-4}$. The systematic error is dominated by the possible model uncertainty. \par Using the same data sample the upper limit has been obtained for the P- and CP-violating decay of $η$ at 90% CL: \par $Br(η\toπ^{0}π^{0}) < 4.3\times10^{-4}$ >.